When packaging products, such as for example food products such as chocolate bars, biscuits and the like, these products are often delivered by the production installation in rows of transversely positioned products. By means of a feed system as described in European Patent No. EP-B-0,124,177, these rows of products can be fed to a packaging machine. The packaging machine comprises a film feed and a folding plate for folding the film around the products. The film tube formed is provided, by means of longitudinal sealing rolls, with a longitudinal seal and, by means of transverse sealing tools, with transverse seals which also cut through the film tube in order to form separate packages containing one or more products.
Dutch Patent No. 172429 describes a drag conveyor with carrier members for the purpose of separating products which bear against one another in the longitudinal direction and feeding them to the film feed at a constant mutual distance, i.e. at regular intervals. On a feed belt, the arriving products are moved towards an adjoining conveyor belt which moves at a higher speed, so that a gap between the products is obtained. A stop mechanism ensures that the products are delivered from the adjoining conveyor belt to the drag conveyor in the correct manner even when starting up the device.
To package products which are supplied in the transverse direction in single packages, it is desirable for the transversely positioned products to be fed to the packaging machine in the longitudinal direction of the products and at regular intervals. For this, it is necessary for the products not only to be changed in orientation but also to be accelerated from an arrival speed which is equal to the product of the product width and the working capacity to a delivery speed which is equal to the product of the product length+intervening space and the working capacity.
A conveyor device for accelerating the products which are supplied in the transverse direction of the products and for delivering products at regular intervals in the longitudinal direction of the products is described in European patent application EP-A-0,711,720. In this device, a series of products supplied in the transverse direction is fed to an acceleration device via a conveyor belt which slopes upwards. The speed of the upwardly sloping conveyor belt is slower than the speed of the conveyor belt situated upstream thereof, so that products which are supplied at arbitrary intervals are conveyed onwards bearing against one another. Beneath the sloping conveyor belt, there is an acceleration device with a number of rotating gripper heads which grip the product fixedly in the region of the end of the conveyor belt and lift it up. After engaging on the product on the transport path, the gripper heads move radially outwards in order to lift the product off the transport path. Then, the product is accelerated by means of the gripper heads and is fed to a transfer device situated above the transport path. By means of the transfer device, the product is accelerated and guided further in the longitudinal direction of the product and at fixed intervals downstream of the acceleration device.
The position of the gripper heads of the known acceleration device is synchronized with the product position of the product to be accelerated by means of a photocell which is positioned in the region of the end of the upwardly sloping transport path. When the gripper head has reached the product to be accelerated, the gripper is displaced radially outwards by means of an electromagnet, in order to come into engagement with the product to be accelerated.
The known device is relatively complex, and consequently is susceptible to faults. When the product is taken up by a gripper head, the difference in velocity which occurs in this process between the product velocity on the sloping conveyor belt and the constant rotational speed of the gripper head can cause an undesirable shift of the product to take place. Furthermore, as a result of detecting the product position on entry and, as a function of this detection, regulating the acceleration device, there is little time available for correcting any errors. Due to the fact that the position detection of the product to be accelerated takes place at a relatively late stage, the capacity of the known device will be relatively limited. Furthermore, owing to the upwardly sloping conveyor belt, the known device takes up a relatively large amount of space and the device has various operating levels, which is not preferred from the point of view of ease of use.
A conveyor device in accordance with the preamble of claim 1 is known from U.S. Pat. No. 5,341,915. In this device, products which have been placed against one another are accelerated and, by means of a wire conveyor, are moved against projections which are moving at a relatively slow velocity. After the products have come to bear against the projections, the wire conveyor passes through amongst the products with a level of slippage. The projections are synchronized with the movement of a further conveyor with projections, so that the products are delivered thereto at fixed intervals.